1. Field of the Invention
The present invention relates to a novel melanogenesis inhibitor containing a piperonyl alcohol derivative and a skin preparation containing the novel melanogenesis inhibitor. The present invention further relates to a novel piperonyl alcohol derivative which is included in the above piperonyl alcohol derivative and which is useful as a component of the novel melanogenesis inhibitor.
2. Description of the Prior Art
Chloasmata, Hatchinson's freckles and skin pigmentation increase and become difficult to remove with aging, and are a large worry particularly to persons of middle or advanced age. The mechanism of crisis of these dyspigmentations is still unknown in many respects; however, they are considered to appear because the melanogenesis function at epidermal melanocytes is activated by the action of sunlight (ultraviolet light) or hormones. Inhibition of such melanogenesis or decoloration of generated melanin is a task in development of fair skin preparation or fair skin cosmetic, and various researches have been made.
In fair skin cosmetics for prevention or treatment of chloasmata, Hatchinson's freckles, etc. of skin, there have been compounded L-ascorbic acid and its derivatives, hydroquinone and its derivatives, pyrones (e.g. kojic acid), placenta extract (see, for example, patent literature 3), etc., all of which are well known to have, for example, an effect of melanogenesis inhibition due to hindrance of tyrosinase activity (see, for example, patent literatures 1 and 2) or an effect of decoloration of generated melanin and further have a fair skin effect.
When the above substances are used singly, however, there are various problems. For example, L-ascorbic acid and its derivatives are insufficient in storage stability and do not exhibit the intended effect sufficiently; hydroquinone and its derivatives have a problem in safety (stimulativeness and allergenicity); kojic acid lacks in storage stability (easy to cause coloring); and placenta extract is slow to show its effect. Thus, each substance has been insufficient. Moreover, their effects of melanogenesis inhibition are insufficient. Hence, development of a compound having a higher inhibition effect has been desired.
Patent literature 1: JP-A-10-29928
Patent literature 2: JP-A-8-119848
Patent literature 3: JP-A-8-104616
The present invention aims at providing a melanogenesis inhibitor which is superior in stability and safety, which has a high melanogenesis-inhibiting effect, and which, when made into a skin preparation, is very stable, safe, and has a sufficient fair skin effect and a sufficient effect for curing skin dyspigmentation.
In such a situation, the present inventors made an intensive study on various compounds. As a result, it was found out that the above aim can be achieved by a piperonyl alcohol derivative represented by the following general formula (1)
wherein R is a straight chain or branched chain alkyl group having 3 to 18 carbon atoms, a straight chain or branched chain alkenyl group having 3 to 18 carbon atoms, or an optionally substituted alicyclic alkyl group.
That is, the present inventors found out that the piperonyl alcohol derivative represented by the above general formula (1) is superior in stability and safety and has a high melanogenesis-inhibiting effect and that a skin preparation containing the derivative is very stable, safe, and has an excellent fair skin effect and an excellent effect for curing skin dyspigmentation. By a further study, it was made clear that the melanogenesis-inhibiting effect of the present invention compound is expressed not by the tyrosinase activity-hindering effect (possessed by conventional compounds) but by a tyrosinase biosynthesis-hindering effect. The present invention has been completed based on the above finding.